This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
One feature of mobile telecommunications systems is the ability to allow a mobile subscriber to travel from one location area (LA) to another LA, and even possibly from one network to another network (commonly known as roaming) while still retaining service. In order to implement such functionality, mobile telecommunications systems typically employ various registers that a mobile subscriber is associated with. For example, a home location register (HLR) can maintain a mobile subscriber's location information and is a register where a mobile subscriber is permanently registered. On the other hand, a visitor location register (VLR) is a register where a mobile subscriber is only temporarily registered.
In traditional circuit switched mobile telecommunications systems such as a Global System for Mobile Communications (GSM) network, each VLR is typically associated with a mobile switching center (MSC), and it is this MSC that actually provides service to the mobile subscriber. If the mobile subscriber travels outside a certain LA or into another network, that mobile subscriber will be temporarily registered with a new VLR and served by a new MSC. In most systems, the HLR will know with which VLR a mobile subscriber is registered. In turn, that VLR knows within which LA the mobile subscriber is presently located. This location information is important because it allows the system to find any mobile subscriber to which a call or communication must be routed. For example, if an incoming call is to be terminated at a mobile station, the system must know which LA the mobile subscriber is currently in so that the call signaling and actual call data may be routed to the correct LA. In Universal Mobile Telecommunications System (UMTS) networks, where both circuit switched service and general packet radio service (GPRS) are supported, serving GPRS support nodes (SGSNs) are the equivalent of MSCs while routing areas (RAs) are the equivalent of LAs. Any given RA then is registered in an associated SGSN for packet switched communications. The MSC/VLR and SGSN make up part of the core network for mobile telecommunications systems.
The capacity of elements used in GSM and UMTS networks are growing. A single MSC/SGSN and its associated VLR may today serve 1 million subscribers. In the near future, multiple millions of subscribers may be served by a single MSC/VLR or SGSN. As discussed above, a VLR is integral to determining where a mobile subscriber is located. If such an element were to fail, the impact on service and revenue would be significant. Moreover, the reputation of a service operator as well as a vendor may be lost for good if a failure were to occur.
If a VLR is reset, all of its temporary data, including the temporary mobile subscriber registrations, is lost. In today's networks, this is not a problem because a GSM core network, for example, is able to use standard MAP procedures. However, if a VLR does not restart properly, e.g. due to some hardware damage resulting from a natural disaster, a back-up system/element must be employed. Such a back-up may simply comprise a redundant MSC/VLR or SGSN, or it may comprise some other MSC/VLR or SGSN that can accommodate the mobile subscribers in a load sharing mode. In the latter case, each mobile subscriber is relocated to another MSC/VLR or SGSN. Unfortunately, if this is done, the HLR associated with the failed MSC/VLR or HLR will not know about the relocation and thus all incoming traffic will fail until the new (target) VLR updates the mobile subscribers' locations to the HLR. To make matters worse, the target VLR does not report to the HLR until either a mobile subscriber initiates a location update (LU), e.g. due to change of location area, or due to periodic location update. Because the periodic LU timer may be set for a period of hours, the break in service would be unacceptable.
In the event of a failure of an HLR “N+X load sharing,” in which an entire HLR database is backed up in a server and downloaded to a redundant HLR if needed, can be used. However, keeping an up-to-date copy of an entire VLR database is very resource consuming and would require a great deal of signaling between VLRs. As such, the only current potential solution for rectifying a failed MSC/SGSN/VLR scenario is to re-home elements such as base site controllers (BSCs), radio network controllers (RNCs), public switched telephone network (PSTN) trunks, and signaling links to a new MSC or SGSN.
It is therefore desirable to provide a system and method whereby MSC/SGSN/VLR resiliency can be achieved without having to copy entire VLR databases, as well as having the option to utilize super-charge technology to accomplish such resiliency.